Method of determining the rust-preventing properties of lubricants



means to present a clean metal surface.

Patented Oct. 19, 1948 METHOD OF DETERMINING THE RUST-PRE- VEN TING PROPERTIES OF LUBRICANTS Carroll H. Van Hartesveldt, Rosemont, Pa., as-

slgnor to The Atlantic Refining Company, Philadelphia, Pa., a corporation of Pennsylvania No Drawing;

The present invention relates to a method, for determined or demonstrating the rust-preventing properties of lubricant compositions, particularly motor oils for the lubrication of internal combustion engines.

Motor oils containing no rust-preventing additives have been found deficient insofar as inhibiting the rusting of metal parts of engines is concerned, and particularly the cylinder walls, pistons, and rings. A recent trend in the manufacture of automotive lubricants has been in the direction of incorporating in the lubricants small quantities of rust-preventives or inhibitors, including oil-soluble sulfonates such as the alkaline earth metal salts of oil-soluble petroleum sulfonic acids, as well as sulfurized oils such as sulfurized sperm oil, and antioxidants such as metal salts of the acid esters of the acids of phosphorus. It has been found that such additives or mixtures thereof, especially the sulfonates and sulfurized oils, have a pronounced effect in inhibiting rusting of engine parts, and it is an object of this invention to provide a simple and rapid method of determining which lubricants are capable of preventing rusting under conditions simulating, to some degree, those which exist in internal combustion engines when not in operation.

In accordance with the present invention, the

testing of the efiicacy of the lubricant in preventing rusting may be carried out directly by exposing a clean ferrous metal test piece to the action of the exhaust gases of an internal combustion engine, or by wetting the test piece with exhaust gas condensate (water containing combustion products), then coating the test piece with the lubricant, and thereafter exposing the coated test piece to air or other gas containing moisture, and noting the condition of the test piece after such exposure. Lubricants containing rust-inhibitors usually give complete protection with respect to rusting, whereas ordinary oils or lubricant compositions containing little or no rustinhibitors permit partial or even complete rusting of the test piece.

In carrying out the present invention, a ferrous metal test piece of any suitablesize and shape, for example, an iron or steel strip about 1 inch by '2 inches and from to inch in thickness, is thoroughly cleaned by sand blasting or other The clean strip is then held in the exhaust gas stream from an internal combustion engine for a short period of time, for example, 2 to seconds, the temperature of the strip or of the exhaust gases being sumciently low as to permit condensation Application August 28, 1946, Serial No. 693,588

5 Claims. (in. 73-86) 2 of the exhaust gas products (mainly water containing products of combustion, e. g., sulfur compounds, and oxygen-containing compounds) upon the clean surface of the strip. The material thus condensed may or may not be visible, but in most cases appears'as a film ora regation of aqueous droplets. The components of the exhaust gases, including sulfur compounds and oxygen-containing compounds, function to accelerate rusting or corrosion of the test strip when same is exposed, in the absence of a rust-inhibitor, to the action of air containing moisture. The wet strip is then coated with the lubricant either by immersing in a body of the lubricant for a short time (5 to 30 seconds) or by applying the lubricant with a brush, swab, or with the fingers. The lubricant coated strip is then drained of excess lubricant, if any, and exposed to air or other gas containing free oxygen and moisture. In the case of lubricants containing no rust-inhibitor, rust appears within a short time, for example, 3 to 5 minutes, and after 24 hours the rusting may be partial or complete. With lubricants containing. rust-inhibitors or rust-preventing additives, little or no rusting is evident even after 24 hours exposure. While the exposure of the test strip is usually made at ordinary temperatures, i. e., F. to F., rusting, if it is to occur, is accelerated by carrying out the exposure at slightly elevated temperatures, for example, F. to F. Therefore, when it is desired to demonstrate the rustpreventing or non-rust-preventing properties of the lubricant in the shortest time, the exposure should be carried out at elevated temperatures of the order of those aforementioned.

In another modification of the present invention, the exhaust gases of an internal combustion engine may be passed through a suitable condenser, and the resulting condensate collected in a glass or other container. The clean metal test strip is then immersed in the container of aqueous condensate for a short period of time, for example, 2 to 30 seconds, and the wet strip is then coated with the lubricant as described above. After draining off excess lubricant, if any, the coated strip is exposed to air or other gas containing free oxygen and moisture, and the condition of the strip after exposure is noted as described above. The test strips or pieces may-be fabricated of any rustable ferrous metal or alloy, such as cast iron, carbon steel, and the like.

The present invention may be further illustrated by the following example, which however, is not to be construed as limiting the scope thereof. Test pieces were prepared by sand blasting SAE -20 carbon steel strips, the strips were dipped Appearance of Test Strip $5 After-- Oil tested 5 minutes 24 hours F. SAE 20 Base Oil 75 partially rusted. 100% rusted (medium). SAE 20 Base OlH-addi- 75 no rust no rust.

tivc. 1

SAE 2e Base on." o rusted in 2 min 100% rusted y). SAE Base OiH-addi- 150 no rust no rust.

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I Additive-l% oil-soluble barium sulfonute+1% suliurize-d sperm oil+i% zinc salt of di-methylcyclohexyl acid tbiopbosphate.

While the method of the present invention is particularly adapted in the testing of hydrocarbon lubricating oils of the type used in internal combustion engines, such method is also applicable in the testing of other lubricants or slushing oils, including mineral oils of different viscosities, compounded mineral oils, animal oils, vegetable oils, and marine oils, or mixtures thereof.

I claim:

1. A method for determining the rust-preventing properties of lubricant compositions, which comprises subjecting a ferrous metal test piece to the action of exhaust gas products of an internal combustion engine, then coating the test piece with the lubricant, exposing the coated test piece to air containing moisture, and noting the condition of the test piece after exposure.

2. A method for determining the rust-preventing properties of lubricant compositions, which 4 bustion engine, then coating the test piece with the lubricant, exposing the coated test piece to air containing moisture, and noting the condition of the test piece after exposure.

3. A method for determining the rust-preventing properties of lubricant compositions, which comprises immersing a ferrous-metal test piece in the condensate from the exhaust gas of an internal combustion engine, then coating the test piece with the lubricant, exposing the coated test piece to air containing moisture, and noting the condition of the test piece after exposure.

4. A method for determining the rust-preventing properties of lubricating oil, which comprises contacting a steel test piece with the exhaust gas of an internal combustion engine for a period of 2 to seconds at a temperature such that exhaust gas moisture containing combustion products is condensed upon the test piece, then immersing the test piece in the lubricating oil, removing the test piece and draining off excess oil, exposing the oil-coated test piece to air containing moisture, and noting the condition of the test piece after exposure.

5. A method for determining the rust-preventing properties of lubricating oil, which comprises I immersing a steel test piece in the condensate REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,770,735 Funk July 15, 1930 1,870,512 Jameson Aug. 9, 1932 2,351,644 Talley et al June 20, 1944 2,405,532 Todd Aug. 6, 1946 

